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Subfossil forest discovered in Zurich

Pine stumps had been preserved in clay for 13 000 years before they were discovered by chance on a construction site in Zurich.
Photo: WSL /Daniel Nievergelt

A Sunday walk led to the discovery of a subfossil forest which has remained intact for over 13,000 years in the Zurich clay, opening new doors for Central European dendrochronology.

Daniel Nievergelt, a dendrochronologist at the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, was just having a look at a building site on the southern edge of the city. He knew there was some justification for hope of a spectacular discovery from his collaboration with his colleague Felix Kaiser, who died in 2012 and who in 1999 had already found subfossil wood during the excavation of the Uetliberg Highway Tunnel. 
He took a closer examination of a few tree stumps that had been discarded as waste timber and found they were pine trees. He sent three samples to the Swiss Federal Institute of Technology (ETH), where C14 datation confirmed his suspicions: the timber was discovered to go back to between 12,846 BP and 13,782 BP.
With the support of the building-site management, the WSL researchers managed to salvage 256 pine-tree stumps. To the knowledge of the researchers involved, the quality and scale of the find are unique worldwide.

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